This invention is related to devices for applying liquid saturated fabric to a surface, and, more particularly, to devices for impregnating glass fabric with polyester resin and applying it to a mold surface.
The present invention was developed for use in handling glass fabric and polyester resin during the construction of glass boat hulls, containers, and other objects generally requiring construction of large glass panels. The handling of the large quantities of glass fabric and polyester resin required to construct such panels gives rise to certain problems to which the present invention is addressed.
The formation of a glass reinforced panel on a mold surface involves essentially three steps. First, a catalyst must be added to a liquid polyester resin. This step typically consists of mixing a small amount of liquid catalyst with a relatively large amount of liquid polyester resin. The relative proportions of catalyst and resin must be precisely controlled and the mixing must be rapid and thorough to ensure uniform and predictable hardening of the resin. Once the resin has been catalyzed, the hardening process begins and there is a limited amount of time during which the catalyzed resin remains sufficiently fluid to permit impregnation of the glass fabric and subsequent application of the saturated fabric onto a mold surface. Because of the limited amount of time available for handling and working the glass fabric after the resin has been catalyzed, mixing of the catalyst and resin is typically done immediately prior to the impregnation of the fabric with the catalyzed resin.
The second step in the formation of a glass reinforced panel involves impregnation of the glass fabric with the catalyzed resin. This process must be precisely controlled so as to ensure complete saturation and wetting of the fabric with the resin, yet avoiding the use of too much resin. The strength weight and other properties of the final glass product are dependent on the relative amounts of glass fabric and polyester resin comprising the product. Generally, optimum characteristics of the final product are achieved when the amount of polyester resin employed is the minimum amount necessary to thoroughly impregnate and wet the glass fabric. The use of too little resin may result in improper wetting and bonding of the glass fabric, with resultant decrease in tensile strength of the final product. On the other hand, the use of too much resin results in the addition of weight, but little additional strength, to the final product. Thus, in practice it is necessary to continuously monitor and control the amount of polyester resin with which the glass fabric is impregnated.
The final step in the process is the application of the impregnated glass fabric onto a mold surface. The mold surface is typically smooth and coated with a releasing agent, for example wax, that permits the final product to be removed without sticking. If the final glass product is to consist of multiple layers of glass fabric, such layers must be successively applied such that they become thoroughly bonded to one another. Where a successive layer is to be applied onto a previously applied layer, this is normally accomplished by applying the successive layer while the previously applied layer is still tacky, that is, before the previously applied layer has hardened.
Where large surfaces are being covered, or where vertical surfaces must be covered, it is usually necessary to assemble scaffolding to accommodate workers who manually work the impregnated fabric onto the surface. This is cumbersome and time consuming because the scaffolding must be assembled and disassembled as the application progresses.
Whether a layer of impregnated glass fabric is applied directly onto a fresh mold surface or onto a previously applied layer, it is necessary that the impregnated fabric be applied smoothly and free of entrained air bubbles. In the application of impregnated glass fabric under the prior art, removal of entrained air bubbles and consolidation of the fabric onto the mold are often the rate limiting steps in the overall application process. Removal of air bubbles is normally accomplished manually, various tools being available for this task. Quality control of this process is difficult to achieve due to the difficulty of inspecting and monitoring the application process during actual operation.
Accordingly, it is an object and purpose of this invention to provide an apparatus which removes entrained air bubbles as it applies an impregnated glass fabric to a surface.
It is a further object of this invention to provide an apparatus which applies impregnated glass fabric free of air bubbles to a surface in a uniform and consistent manner, thereby improving upon the quality of the final product over that which may be had when air bubbles are manually removed.
It is a further object of this invention to provide an apparatus which applies impregnated glass fabric and removes entrained air bubbles simultaneously and in a single pass of the applicator, thereby increasing the overall rate at which a glass reinforced product can be produced.
It is a further object of the present invention to provide an apparatus that can not only apply an impregnated glass fabric to a surface and remove entrapped air bubbles but, as importantly, that can also consolidate the glass fabric so applied onto the mold surface or with a previously applied layer of fabric without manual sweeping or similar additional manipulation of the fabric, thereby eliminating the need for manual consolidation labor, eliminating the need for scaffolding that must otherwise be employed within the mold to support the personnel required for manual consolidation of the fabric, and thus significantly decreasing the time required to apply and consolidate the impregnated fabric.
Finally, it is an object of this invention to provide an apparatus whereby a single individual operating from a control console can direct the entire process from mixing and impregnation of the resin to final application and consolidation of the impregnated glass fabric onto a surface.